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Gelled propellant components

DDE

By DDE
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DDE

DDE

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So, while I imagine a lot here have read Clarke’s general description of the gelled propellant business, I’ve recently skimmed over Sutton. Since it’s a mid-naughts book, it is more complete - and makes references to a relatively recent (early-naughts) Northrop program that tried to make a tactical rocket using MMH-IRFNA. Sutton doesn’t really cover the gelling agents, and stops at saying they used carbon; several other sources point to boron and aluminium as performance-boosting gelling agents. Their own paper being referenced is paywalled, and my own chemistry education stopped in high-school with a teacher who thought titanium aluminide is impossible.

The big question I have is how can one gelling agent be used for both reducing and oxidizing environments, especially seeing as being in dust form rapidly increases their reactivity, and some of them, like aluminium, are pretty reactive to begin with.

And the minor question is why they used carbon if the main selling point of hypergols over solids is an inherent lack of a smoke trail.

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DDE

DDE

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7 hours ago, YNM said:

Gelling ? Are they still getting off pumps ? Or is it like, a solid hypergolic stuff (that seems dangerous...)

A gel by definition caves in to pressure. Pump and injector design is non-trivial, but it’s still a liquid-propellant motor.

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magnemoe

magnemoe

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3 hours ago, kerbiloid said:

Why anybody would need it?

An gelled acid sound more useful than gelled rocket fuel. 
It would be nice for all sort of surface treatments, lots of body care products are gelled for the same reason. 

In an rocket there g forces is between +3 to 0 g, atmospheric pressure goes to zero as you climb not so much, now hybrid as in solid+ liquid rockets are pretty smart. 

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YNM

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10 hours ago, DDE said:

A gel by definition caves in to pressure.

There are minimum limits to what the pressure will be. Gells don't cave in, they just have some strain modulus.

TBH, I don't see much use for such gells, unless the gelling agent increases performance (read : more violent reactions) of the propellant. As mentioned, they're much denser than water already, and adding more matter reduces their efficiency (albeit there's some possibility of ISP enhancement if it's far lighter than the material they're gelling).

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DDE

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12 hours ago, kerbiloid said:

Why anybody would need it?

1 hour ago, YNM said:

There are minimum limits to what the pressure will be. Gells don't cave in, they just have some strain modulus.

TBH, I don't see much use for such gells, unless the gelling agent increases performance (read : more violent reactions) of the propellant. As mentioned, they're much denser than water already, and adding more matter reduces their efficiency (albeit there's some possibility of ISP enhancement if it's far lighter than the material they're gelling).

A key selling point of gelled fuels, especially gelled hypergols, they don't spill, and thus behave similar to solid fuels that have displaced them while retaining their throttleability, refire capacity and superior performance.

They also don't slosh, and need less ullage, which is why someone decided to bubble ClF3 through liquid F2 to produce a deep space propulsion stage (according to Clarke, ClF5 didn't produce a gel, for some reason).

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YNM

YNM

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6 minutes ago, DDE said:

... they don't spill ... while retaining their throttleability, refire capacity and superior performance.

 

... They also don't slosh, and need less ullage ...

In which case, I intoduce you : Green Propellant.

 

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DDE

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2 hours ago, YNM said:

In which case, I intoduce you : Green Propellant.

Hideously reduced performance (monoprop, is it even hypergolic with storeable oxidizers?), and what's the freezing temperature of this unspecified propellant? That's why tactical rockets use IRFNA and not pure NTO.

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YNM

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8 minutes ago, DDE said:

Hideously reduced performance (monoprop, is it even hypergolic with storeable oxidizers?), and what's the freezing temperature of this unspecified propellant? That's why tactical rockets use IRFNA and not pure NTO.

I guess it's somewhere in the papers if you find any.

Also, I think it's being researched by the military itself ?

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magnemoe

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1 hour ago, DDE said:

Hideously reduced performance (monoprop, is it even hypergolic with storeable oxidizers?), and what's the freezing temperature of this unspecified propellant? That's why tactical rockets use IRFNA and not pure NTO.

That one is an monoprop yes but for an monoprop it has good performance. Main benefit is that its easy to work with.
This is important for cheaper satellites, 

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DDE

DDE

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2 hours ago, kerbiloid said:

Or AK-20, AK-27, ...

Let's not confuse the 'Muricans here. For example...

2 hours ago, magnemoe said:

This is important for cheaper satellites, 

I started off thinking about tactical missiles, and kerbiloid's links only further steered me towards high-performance military missilery - it concerned Soviet Aluminol UDMH-Al fuels for even more compact SLBMs.

Performance is paramount, ease of fueling is not - so long as, unlike some Soviet missiles, you don't need to fuel and unfuel all the time, which is an anomaly.

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kerbiloid

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25 minutes ago, DDE said:

fuels for even more compact SLBMs.

Though as we can see in the searched results it was rejected long ago due to problems. Like Green Dragon and so in USAF.

26 minutes ago, DDE said:

you don't need to fuel and unfuel all the time, which is an anomaly.

Only in early 1960s rockets. Since 1970s they stay fueled for decades without gelling.

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DDE

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17 minutes ago, kerbiloid said:

Only in early 1960s rockets. Since 1970s they stay fueled for decades without gelling.

I'm not even talking about gelling. Apparently, something about AK-27I or Tonka caused Kh-22 AShMs to need fueling and unfueling all the time, to the absolute dread of ground crews.

5 minutes ago, YNM said:

Current Tridents apparently don't use the "standard" NTO/UDMH.

Did you miss the "Soviet" bit?

Bulava's solid motors have caused a lot of controversy, and it's not designed by the primary SLBM developer - Makeyev (in return, Makeyev dabbles into ground-based missiles with Sarmat). A solid SLBM has had to be shoved down the throat of both the Navy and designers - heck, Makeyev gave us some of the only mixed solid first stage/liquid upper stage SLBMs out there, that's how much they liked their UDMH-NTO.

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DDE

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@YNM

Not to mention, Makeyev take pride in leaving zero empty space in their rockets, to the point of obsession.

Those things around the third stage engine of this Lainer are the nukes. Yes, they're upside down. Yes, the tanks of lower stages are wrapped around upper stage engines. And yes, the third stage engine is jettisoned following the initial burn.

Komponovochnaya_shema_rakety_Layner.jpg

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YNM

YNM

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32 minutes ago, DDE said:

Did you miss the "Soviet" bit?

Well the book you read wasn't really !

Also, those looks... interesting.

 

TBH I don't know much for the gelling. All I know is that gells aren't easy to work with. They're avoided where possible (unless you can't avoid them, like soil). So... yeah, I'm not sure why would you choose something that can shrink rather than just a liquid.

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mikegarrison

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35 minutes ago, YNM said:

TBH I don't know much for the gelling. All I know is that gells aren't easy to work with. They're avoided where possible (unless you can't avoid them, like soil). So... yeah, I'm not sure why would you choose something that can shrink rather than just a liquid.

The food industry works with gels all the time. I have seen articles about university engineering labs collaborating with their food science labs to learn how to handle gels.

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